honestly for a Japan trip you want the Sigma 28-70mm f/2.8 DG DN Contemporary for L-Mount. Ive tested both and while the Art version is technically sharper in the corners with better flare resistance, the 470g weight of the Contemporary is a lifesaver when youre walking 20k steps. It isnt really compromised unless you need that 24mm wide end. The PDAF on your S5II keeps it super snappy tho.

You absolutely need something reliable for a trip like this! The Sigma 24-70mm F2.8 DG DN Art is fantastic because the build quality and weather sealing are so much better than the smaller version.

• Sigma Art: Incredible optics, professional build quality.
• Panasonic LUMIX S 24-105mm F4 Macro OIS: Best stabilization, super dependable native performance. I love the Sigma for its constant f/2.8 aperture, its amazing in those narrow Tokyo alleys!

Tbh I'd just stick with a lens from Panasonic. I tried a third-party zoom once during a family trip and it was such a letdown. The autofocus kept hunting in low light and I missed so many candid shots. It was super frustrating because people online hyped it up, but it just didnt feel right on the S5II. The weight was fine but the results were just kinda meh compared to what I expected from the native glass.

• native lenses usually have better weather sealing
• the autofocus is way more reliable
• you wont have weird firmware glitches I really wanted to love the cheaper alternatives but they just arent as good as I expected. Just get any fast zoom from Panasonic and youll be way happier.

Just saw this thread. Unfortunately, I've had some annoying reliability issues with the cheaper third-party zooms on my S5II that really soured me on them for travel. The AF is usually snappy until it suddenly isnt, usually right when the lighting gets tricky in those narrow alleys. Quick question tho, are you planning on doing much handheld video or mostly just stills? The way the stabilization works between the body and lens really changes which one I'd recommend for those long walking days. If you want something that actually feels professional and wont fail you if you get caught in a Kyoto downpour, consider these:

• Panasonic LUMIX S PRO 24-70mm F2.8
• Honestly, check the used market. You can find them around $1300 and the build quality and dual AF motors are far superior to the Sigmas for critical work.
• Panasonic LUMIX S 28-200mm F4-7.1 MACRO OIS
• I know you asked for f/2.8, but for a Japan trip, the range and native reliability of this thing are hard to beat when you want to pack light. tbh I would stay away from the Contemporary line if you're worried about compromises... the weather sealing just feels like a gamble when you're that far from home.